Rotary actuator



May 7, 1957 ROTARY ACTUATOR 2 Sheets-Sheet l Filed April l, 1954 m T r v www ,m WG 0 y l l W M mi d N. u m W Mln s m w Il IIlI 0 m. ww Im o* H m -UH v N 7 J ww W 1| N A Nw NN N\E. i wu! I x cx W `i S on n N H l \\l ww I. I' me n g Nm l? vw. wm E o. @N wm wm ow May 7, 1957 H. M. GEYER ETAL 2,791,128

ROTARY ACTUATOR Filed April l. 1954 2 Sheets-Sheet 2 1NVENTO&

lk Howard M. Geyer By James N. Toot/e Stat-g Patent This invention.pertainsaitorotary-l actuators;` and aparticallarly--tol a rotary actuator`- withcvanti'fbacklash. means.`

Here'tefre;I preciser-angular adjustment of-.;a-control devicea has .been -diticult ifi not. impossible, to:obtairr .by meansof-.raarotary actuator. This problemhas been attributedf..to f the back-lash vinherentA inrotaryi actuators presently tused tofelect.-angularr'adjustment o: control devicesi One.y ofy the salient features of 'this invention residesinethe fact that, backlash betweenthe-4 relatively rotatahleeparts.y of aan. actuator .ist subst-ar'rtially-y eliminated. Accordingly, :among` our objects arel thewrprovisi'on Yot'ya 'rot-ary; actuator including means for eliminatingl backlash .f

between relatively :rotatable parts; the i further l provision of. means-.-for elminatingilbaeklashz between;=r relatively rotatableemembers having; helical spline f teetlgg, and; the stilhffurtheryprovisiona-Of meansafon misaligning {thesteeth of one .helicallysplined .member slof-fas .to"eliminatefibaek laslrbetween. a; plurality.ofrrelatil/elyrfrotatablehelically splinedmembers..

The aforementionediandfother objects .areaccomplished in the present invention by separating one helically splinedlmember, into two sectionsainsertingfshims between the two sections, andthereafter. assembling the two sections so thatth spline 'teeth of the member are misaligneda: predetermined amount: `Sggle'cicallyl,'-the. act-uator; embodying the.. helical. spline.,ar'rangern'ent= of? fthis inventioir-.comprisesa cylinder` .having-disposed?therein a reciprocable piston... capable.. of .fluicn'pressurec'. actuation in both directions. The piston has attached thereto an axially extending skirt having a portion with ,internal and external helical splines. The splined portion of the skirt is originally machined as an integral unit and thereafter divided into two annular sections. A plurality of shims are interposed between the two axially spaced splined sections, after which the two sections are assembled to form a spline member having misaligned teeth.

The external misaligned splines of the piston skirt engage internal helical splines formed on a portion of the internal piston periphery, and the internal misaligned splines of the annular skirt engage helical splines formed on a member rotatably journaled in the cylinder. The actuator piston divides the cylinder into two chambers, which are connected with a pair of ports so that pressure uid may be admitted to either chamber so as to effect reciprocable piston movement. The cylinder is normally restrained -against rotation such that upon reciprocable movement of the piston, the piston has imparted thereto a slight angular movement due to the helical spline connection between the skirt and the cylinder walls. During reciprocable movement of the piston, rotation is imparted to the output member of the actuator which is equal to the sum of the rotary movement produced by the helically :splined surfaces of the cylinder, the piston skirt and the -output member.

Further objects and advantages of the present inven tion will be apparent from the following description, yreference being had to the accompanying drawings Where 'ice in A. a `preferred .fembodiment .f of .the present. inventionis clearly-shown.:

Inthedrawings: Y y

Fig; `1f` is. a vlongitudinal.y sectional. view voffanuactuator constructed:r accordingtofthe present' invention.V`

Figa.; 2 Y-is a. fragmentary view, ypartly l in. isection. and partly in elevationl,'illustrating therhelical-spline arrange.- ment.

Fig. 3 is an.-enlarge di1fragmentary\ view,..partlyin .sectionnand partlyin elevations depicting, the mannen-in which. baeklashbetweenthe helically ysplinedt members. is eliminated. p v

With.-.particular reference-to fFig. 1 an\-actuator-.10-is ,shownlincludingg afzcylinder 12,'Vv -oneendey of Iwrhiclrisclosed by a ycap member 14 having formed therein an? extend port; 16 and '.carryinggapair. of. spaced "fbrackets.-- 18x by which mea-nsf' the vactuator *cy-linden .may-f bef yattaclredvto any; suitablyjixedf` support, not shown.k The-"actuator cylinder f1-2. fis adapted,toi-bet-restrainedf against all. movefmen't,... both linear. and f rotary by the- 4interconnection/.olf

bracketmembers 18 with a rxedisupport.. Th'eifcylinder 12 #has f disposed thereinai, reci-procable--pistonY 204 which divides-acylinder intoanextend chamber'22'iandra. retract char'nber;124,l4 the cylinder also hav-ingier-l retract porti-26 formed; thereirn.

The:V piston IZtlfsealin'glyv engages; the. internal'rwallsxof `theres/lindenMaand `hasthrea'dedly connectedrthereto and movable.- therewith; an! annular skirt; 28;AVV Ther-*annular sleirt28l=ncludesf two sections:.3(l*ar1d:4(;v As' Lisvseen more particularlyrin .-Fig'. 2,.`the"section:3.0 isz formedzwith internalhelical; spline teeths323and; external helical spline teeth34, while the section #10i-'is formed with.r internal helicalspline: teeth. 42 'andexternal helical. splineteeth 44.-. Originally,v .the skirt4 28 is made; as: anA integrall=unit having: helically.VV splinedl sections 30fa'nd'40; Thereafter,

the;rsplinedlfportionfof. wthe .annular *skirt splits. Tinto :two sectionsiand a-'fpluralityli of '.spacing.means, or shims; 36 arefsinsertedl'therebetween after-which, the ltwo sections 30 and 40 .are .reassembled by means of a plurality of cir-cumferentially spaced bolts.38 andi dowel"pi1isvf46v In soi doinggifthe externalf helical'splinel teeth :342and1 44, as wellas@thewinternalhelical spline .teethr -`3`2 land-f42ar`e Imisaligned a predetermined amount, as depicted in Figs. 1 and 2.

The external helical spline teeth on sections 30 and 40 engage internal helical spline teeth 48 formed on the 'inner periphery of the cylinder 12. The internal helical spline teeth of sections 30 and 40 engage helical spline teeth 50 formed on the external surface of an actuator output member 52.

As shown particularly in Fig. l, the actuator output member 52 is formed with a shoulder portion 54, which sealingly engages the cylinder walls, the member 52 being rotatably supported within the cylinder 12 by ball bearing means 56 and 58. The outer races of ball bearing means 56 and 58 are retained in position by an annular ange member 60, which is bolted to the cylinder, as shown in Fig. l.

The actuator output member 52 is also formed with a series of :straight splines 62, which are engaged by internal straight splines 64 of an annular member 66 having an externally straight splined surface 68. The actuator output member 62 may be connected to any suitable load device through the member 66. Moreover, lineal movement of the actuator output member 62 relative to the cylinder 12 is precluded by reason of the member 52 being assembled with the member 66 through a nut and bolt arrangement 70 and a washer 72. Thus, the members 52 and 66 are drawn tightly against the inner races of the ball bearings 56 and 58 so as to prevent axial movement of the member 52 relative to the cylinder 12.

With particular reference to Fig. 3, the manner in which l 3 the misallgned spline teeth of the sections 30 and 40 eliminate backlash betweenthe several relatively rotatable members will be described in greater detail. From an inspection of Fig. 3, it may be seen that the helical spline teeth34 and 44,by reason of being heldin axially spaced relationship by the shim means 36, are misaligned a predetermined amount. The axial spacing of the sections 30 and 40 is chosen so that the helical spline teeth 34 and 4heretofore inherent in a helical spline connection has been substantially eliminated. Accordingly, the `position of foutput member S2 and any control device associated therewith may be precisely controlled by movement of l the piston 20. Operation of the actuator disclosed hereinis substantially as follows, reference being had to Fig. l. Upon the application of pressure uid to the retract chamber '24 through the retract port 26, while the extend chamber 22 is connected to drain through extend port 16, the

piston 20 will move to the right, as viewed in Fig. 1. Linear movement of the piston 20 is accomplished by slight annular movement thereof due to the inner` action Aof the helical splines on the skirt 28 with the cylinder wall. Moreover, this slight annular movement of the piston 30 and the cylinder 28 will be imparted to the output member 52 such that the output member will be rotated with a movement that is the sum of `the rotation .caused by spline teeth 48 and 34, 44, and 32, 42 and 50.

Moreover, VVby reason of the misaligned helical spline teeth on the annular skirt sections 30 and 40, the output memberv 52 will be accurately `positioned without any backlash between the relatively rotatable parts. Conversely, when pressure iluid is applied to extend chamber `22 and retract chamber 24 is connected to drain, the output member `52 will be rotated in the opposite direction.

While the embodiment', of the present invention as herein disclosed, constitutes a preferred form, it is tobe understood that other forms might be adopted.

What is claimed is as follows:

-l. A rotary actuator including in combination, a cylinder, a reciprocable` piston disposed in the cylinder, said cylinder having internal helical spline teeth, an annular skirtrigidlyconnected to said piston and having internal and `external helical spline teeth, a member rotatably journaled in said cylinder having external helical spline teeth, the external helical spline teeth on said skirtmating with the internal helical spline teeth on said cylinder, the internal helical :spline teeth on said skirt mating with the external spline teethon said member whereby rotation will be imparted to said member upon reciprocation ofsaid piston, an annular Velement having internal and external helical spline teeth, a plurality of shims disposed between said annular element and an end of said annular skirt, and means for rigidly connecting said annular element to said skirt to stagger the relationship between the helical spline teeth on the annular skirt and the annular element and thereby eliminate backlash in the helical spline connections between Ithe cylinder, the skirt, the annular element and the rotatable member,

2. A rotary actuator including in combination, a cylinder, a reciprocable pistonfdisposed in the cylinder, said cylinder having internal helical spline teeth, an annular skirt rigidly connected to said piston and having internal and external helical spline teeth, a member rotatably journaled in said cylinder having external helical spline teeth, the external helical spline teeth on said skirt mating with the internal helical spline teeth on said cylinder, the internal helical spline teeth on said skirt mating with the external spline teeth on said member whereby rotation willbe imparted to said member upon reciprocation of said piston, an annular element having internal and external helical "spline teeth, shim means disposed between said annular element `and an end of said annular skirt, and means for rigidly connecting said annular element to said skirt` to stagger the relationship between the helical spline teeth on the annular skirt and the annular `element and thereby eliminate backlash inthe helical spline connections between the cylinder, the skirt, the annular element and the rotatable member.

References Cited in the tile of this patent UNITED STATES PATENTS Wright Oct. 28,` 1947 warf- 

